Passing selected values from gridview to another page

I am not sure the issue here, but the ASP Tag <asp:ButtonField> is not a known element. I am using ASP.net 2.0. If you are using 1.0 I am wondering if it was removed??

Here is my gridview, you can see I have a template field with a button on it that I have assigned an on-click event to. When this fires i set a session variable = to the selectedvalue of the gridview, problem is that if the user doesnt first make a selection, then the selectedvalue of gridview1 = nothing.

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource1" HorizontalAlign="center" Width="500px" EmptyDataRowStyle-BorderStyle="None" EmptyDataRowStyle-BorderWidth="0" DataKeyNames="KEYID">
  <Columns>
    <asp:CommandField ShowSelectButton="True" />
    <asp:BoundField DataField="KEYID" HeaderText="Listing #" InsertVisible="False" ReadOnly="True" SortExpression="KEYID" />
    <asp:BoundField DataField="txtAddress" HeaderText="Address" SortExpression="txtAddress" />
    <asp:BoundField DataField="isActive" HeaderText="Active" SortExpression="isActive" />
    <asp:TemplateField>
      <ItemTemplate>
        <asp:Button ID="Button2" runat="server" Text="Upload Pictures" OnClick="Button2_Click" />
      </ItemTemplate>
    </asp:TemplateField>
  </Columns>
  <RowStyle HorizontalAlign="Center" />
  <EmptyDataRowStyle BorderStyle="None" BorderWidth="0px" />
</asp:GridView>

Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)

        Session("KEYID") = GridView1.Selectedvalue
        Server.Transfer("uploadpictures.aspx")

    End Sub

BTW.. im programming in  VB

i think if this can be converted to VB it will work for me..

OnRowCommand="GridviewUnAssigned_OnRowCommand"

    protected void GridviewUnAssigned_OnRowCommand(Object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "status")
        {
            // Convert the row index stored in the CommandArgument
            // property to an Integer.
            int index = Convert.ToInt32(e.CommandArgument);

            // Retrieve the row that contains the button clicked
            // by the user from the Rows collection.
            GridViewRow row = this.GridViewUnassigned.Rows[index];

            //convert the id data in cell 1 to int
            int id  = Convert.ToInt32(row.Cells[0].Text);
            Session["appraisalfileid"] = id;
            Server.Transfer("page2.aspx");
        }
    }

Going through this I have converted it to VB myself, though I am getting an error which doesnt make sense, since the code is basically copied from the Microsoft site itself http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.rowcommand.aspx

"Input string was not in a correct format."

that happens on this line ..

Dim myindex As Integer = Convert.ToInt32(e.CommandArgument)

this is the whole sub routine..

Protected Sub GridView1_RowCommand(ByVal sender As Object, ByVal e As GridViewCommandEventArgs)

        If e.CommandName = "Upload" Then

            'Convert the row index stored in the CommandArgument
            'property to an Integer.
            Dim myindex As Integer = Convert.ToInt32(e.CommandArgument)

            'Retrieve the row that contains the button clicked
            'by the user from the Rows collection.
            Dim row As GridViewRow = GridView1.Rows(myindex)

            'convert the id data in cell 1 to int
            Dim id As Integer = Convert.ToInt32(row.Cells(2).Text)
            Session("KEYID") = id
            Server.Transfer("page2.aspx")
        End If
    End Sub

it seems that there is no value being passed into CommandArgument. looking at the debugger, it shows "0"

i just got it.. completed code as follows..

Protected Sub GridView1_RowCommand(ByVal sender As Object, ByVal e As GridViewCommandEventArgs)

        If e.CommandName = "Upload" Then

            'Convert the row index stored in the CommandArgument
            'property to an Integer.
            Dim myindex As Integer = Convert.ToInt32(e.CommandArgument)

            'Retrieve the row that contains the button clicked
            'by the user from the Rows collection.
            Dim row As GridViewRow = GridView1.Rows(myindex)

            'convert the id data in cell 1 to int
            Dim id As Integer = Convert.ToInt32(row.Cells(1).Text)
            Session("KEYID") = id
            Server.Transfer("uploadpictures.aspx")
        End If
End Sub

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource1" onrowcommand="GridView1_RowCommand" HorizontalAlign="Center" Width="500px" EmptyDataRowStyle-BorderStyle="None" EmptyDataRowStyle-BorderWidth="0" DataKeyNames="KEYID" EnableViewState="False">
                                <Columns>
                                    <asp:CommandField ShowSelectButton="True" />
                                    <asp:BoundField DataField="KEYID" HeaderText="Listing #" InsertVisible="False" ReadOnly="True" SortExpression="KEYID" />
                                    <asp:BoundField DataField="txtAddress" HeaderText="Address" SortExpression="txtAddress" />
                                    <asp:BoundField DataField="isActive" HeaderText="Active" SortExpression="isActive" />
                                    <asp:ButtonField ButtonType="Button" CommandName="Upload" HeaderText="Pictures" ShowHeader="True" Text="Upload Pictures" />
                                </Columns>
                                <RowStyle HorizontalAlign="Center" />
                                <EmptyDataRowStyle BorderStyle="None" BorderWidth="0px" />
                            </asp:GridView>

there are other ways to do it but that was the quickest that sprung to mind... working long hours and not enough for ee...